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Abstract:
Concerted efforts are being made to understand the current and past
processes that have shaped Antarctic biodiversity. However, high rates
of new species discoveries, sampling patchiness and bias make estimation
of biodiversity there difficult. Antarctic continental shelf benthos is
better studied in the Ross, Weddell and Scotia seas, whilst the Amundsen
Sea has remained biologically unexplored largely because of severe ice
conditions year-round. Here we report results from examination of the
first benthic biological samples taken from the Amundsen Sea. We compare
relative abundance, taxonomic richness and faunal composition of isopod
families, and genera and species within two example families (i.e.
Desmosomatidae and Nannoniscidae) from the Amundsen Sea with
complementary sampling from the Scotia Sea. Benthic samples were taken
from inner and outer Pine Island Bay (eastern Amundsen Sea) sites using
an epibenthic sledge at 500 m. Similar samples were also collected from
15 Scotia arc sites at 160- to 500-m depths. The relative abundance of
isopods in the Amundsen Sea samples was high and surprisingly less
variable than across samples in the Scotia Sea. The abundance structure
of isopods at family level was compared across different Antarctic seas.
We found that in the Amundsen, Scotia and Ross Seas two families
dominated abundance. In contrast, isopod abundance reported in the
literature from Weddell Sea samples was much more evenly distributed
across families. The Amundsen continental shelf isopod fauna appears to
be rich, with 96% of individuals belonging to currently undescribed
species. Most of the genera have either been described or found
elsewhere, but for many of these genera it is the first time they have
been recorded away from the Antarctic continental slope or deep sea. The
Amundsen Sea assemblages differed greatly from the Scotia Sea sites in
terms of both composition and (species and generic) richness. This was
largely due to high consistency between samples compared with the highly
variable Scotia Sea samples. Thorough biological analyses implementing
well-structured geographic sampling regimes and the application of
phylogeographic analyses on a variety of taxa are required to further
explore the geographic structure of biodiversity and the evolutionary
history of the Amundsen Sea.
